Author Topic: Ductless HVAC Systems  (Read 17350 times)

Offline stokester

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Ductless HVAC Systems
« on: May 03, 2019, 06:06:37 PM »
I'm considering adding a heat and air system to my shop.

It's about 2.5 bays downstairs and a workshop upstairs with the only insulation in the upstairs ceiling and walls.  Currently the 220v window unit upstairs keeps it comfortable upstairs in the summer and a couple of kerosene heaters keep it tolerable in the winter.  Downstairs stays relatively cool in the summer but cold in the winter.

The Mitsubishi split system air pumps may be a solution to keep the garage temperature tolerable and cut down on humidity during the early spring and fall days when the outside moist air warms up only to condense on the floor and my tool boxes because of the night cold soak.

So does anyone have experience with these systems and can I use it to stabilize the temperature without breaking the bank?  I know they are pretty efficient but I don't want it to be so expensive to operate that I can't use it often enough to be worth the expense.  Secondly is there a better solution?
Nick
Yorktown, VA

Offline bonneyman

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Re: Ductless HVAC Systems
« Reply #1 on: May 03, 2019, 08:30:49 PM »
OK, you're looking to use a mini-split the way they were originally designed to be used: not as the primary source of heat/cool. (i.e. if the thing quits it's not going to be critical)
Lots of brands out there with different features and gimmicks, some work better than others as I hear. No direct experience, although I did install one on a computer room like 16 years ago. Did a decent job of keeping the computer servers running cool, don't know what the running costs were.
Some of the new ones are inverter (i.e. variable speed compressor) technology, which promises ultra-high efficiency and low energy costs. Can't speak to any operating characteristics on those though.

You might want to consider "portable" A/C units. They're about the size of a standard luggage bag with wheels, and all they need is access to a window or hole for in and out airflow and a 115 volt plug. Added bonus is you can wheel them into the house if you're having an issue with a hot room or want something just to cool the bedroom at night without running the house A/C.
Like these:
https://www.popularmechanics.com/home/g3066/best-portable-air-conditioners/

Hope this helps!

Offline Matt_T

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Re: Ductless HVAC Systems
« Reply #2 on: May 03, 2019, 11:51:33 PM »
So does anyone have experience with these systems and can I use it to stabilize the temperature without breaking the bank?  I know they are pretty efficient but I don't want it to be so expensive to operate that I can't use it often enough to be worth the expense.

They're definitely going to be your cheapest running cost for cooling. For heat they're generally cheaper than everything but wood and natural gas. Though that can vary a bit depending on local energy prices. So it's among the cheapest options. Whether that's cheap enough depends on the building..........................

I'm running two cheap 12K 15 SEER inverter units in my 1,400 SF house for primary heat and air. Place was built in the early '50's so no insulation in the walls and crap insulation in the attic. But the place is pretty tight. T&G everything including the roof deck. North Miss so summers probably hotter/longer/humider and winters shorter/milder than yours. IIRC you're somewhere in VA?

Anyways best as I can figure last summer cooling used 2,000 kWh and this winter heat was 2,100 kWh plus about 50 gallons of propane for backup heat. That's under $500 for the year at my local energy prices ;D

Secondly is there a better solution?

First off it sounds like you've got a serious air leakage problem since everything is getting wet when the temp swings. Do what you can to seal up the building or you're going to be fighting humidity leaking in and energy/money leaking out.

Second insulate the downstairs if you can do it for reasonable money and time. My place I will insulate the attic once I get done with rewiring. The walls maybe, at some point, because it'd require ripping the siding off. And I'd likely never see a return on investment from insulating the walls. If I do it it'll be to kick the mean radiant temperature up in the winter.

Once you get as much of the above done as you reasonably can then start looking at climate control. Based on your description of the shop a minisplit downstairs and keeping the window shaker upstairs would be a good starting point.

And if you do go with mini splits consider tooling up to install them yourself. You can buy everything for what a lot of HVAC pros charge for one install. And some of it crosses over to automotive A/C so you can get more use out of it.

Offline stokester

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Re: Ductless HVAC Systems
« Reply #3 on: May 04, 2019, 07:23:23 AM »
Secondly is there a better solution?
First off it sounds like you've got a serious air leakage problem since everything is getting wet when the temp swings. Do what you can to seal up the building or you're going to be fighting humidity leaking in and energy/money leaking out.
[/quote]
Thanks Matt, good info.

The building is really pretty tight.  The condensation I was referring to is when I open up the overhead door in the morning after a cool night which leaves the concrete slab and all inside cool, a warm/moist day will cause sweating on these surfaces.  My thought is that a system to keep the inside temp at least 50deg or so would prevent this.  I've worked downstairs on very hot/humid days without much discomfort using just a shop fan so I don't need to keep it house-comfort cool and upstairs I have the "window shaker" when I work on the electronics bench.

Long-term plan is to insulate but I'd like to get the HVAC in first.
Nick
Yorktown, VA

Offline bonneyman

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Re: Ductless HVAC Systems
« Reply #4 on: May 04, 2019, 11:20:27 AM »
"And if you do go with mini splits consider tooling up to install them yourself. You can buy everything for what a lot of HVAC pros charge for one install...."

IDK. You could probably get by without a torch setup but a good vacuum pump ain't cheap. Plus, if you're just an average DIY, there's alot of HVAC stuff that you'll have to guess at. And - if you have any problems - many companies hassle you with the warranty if you didn't have a licensed guy do it. Get a reputable dealer to install it and you'll be miles ahead.

Offline stokester

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Re: Ductless HVAC Systems
« Reply #5 on: May 04, 2019, 02:21:43 PM »
I've got an HVAC company that has taken care of my house for over 20 years and the Trane system installed over five years ago has been fault-free.  I have a maintenance contract with them for twice a year checkups and will use them for any new system I purchase.  For me it is worth any amount I would save.
Nick
Yorktown, VA

Offline slip knot

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Re: Ductless HVAC Systems
« Reply #6 on: May 04, 2019, 06:02:35 PM »
When I was looking at this I found most of the warranties are void if a DIY installed it. 

Offline Matt_T

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Re: Ductless HVAC Systems
« Reply #7 on: May 04, 2019, 09:25:00 PM »
The building is really pretty tight.  The condensation I was referring to is when I open up the overhead door in the morning after a cool night which leaves the concrete slab and all inside cool, a warm/moist day will cause sweating on these surfaces.  My thought is that a system to keep the inside temp at least 50deg or so would prevent this.  I've worked downstairs on very hot/humid days without much discomfort using just a shop fan so I don't need to keep it house-comfort cool and upstairs I have the "window shaker" when I work on the electronics bench.

Long-term plan is to insulate but I'd like to get the HVAC in first.

OK if the condensation is only happening with the door open you should be alright. Downside of doing HVAC before insulation is you're either going to be living with undersized equipment until you insulate or oversized afterwards. Inverter minisplits handle oversizing better than most systems but the closer you can size them to the cooling load the better the humidity control. Another thing regards sizing is you'll probably need to go with a "hyper heat" mini to get the heating you need without oversizing for AC.

Regards whether heating to 50* will be enough for your condensation problem try plugging in the outdoor temperature and RH you're having problems with at the following link. What it calculates for dew point is the temperature you need inside the shop to prevent condensation. Also a lot of minis don't really have a good way of handling low indoor temperature heating. A lot of them jump from a frost protection mode to normal heat starting in the 60*+ range with nothing in between.

http://bmcnoldy.rsmas.miami.edu/Humidity.html

Offline Matt_T

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Re: Ductless HVAC Systems
« Reply #8 on: May 04, 2019, 10:26:35 PM »
IDK. You could probably get by without a torch setup but a good vacuum pump ain't cheap. Plus, if you're just an average DIY, there's alot of HVAC stuff that you'll have to guess at. And - if you have any problems - many companies hassle you with the warranty if you didn't have a licensed guy do it. Get a reputable dealer to install it and you'll be miles ahead.

No torch needed. Just bending the lineset and 45* SAE flares for the ends. I did my first two installs hand bending but I do have a lot of experience hand bending tube so it might be best for a DIYer to buy a tubing bender. The flares I use a Ridgid flaring tool which wasn't expensive. And you're supposed to torque the flares so figure in a few bucks for a couple 3/8" drive crowsfeet if you want. Under $200 for all of this.

The vacuum pump I just googled my Yellow Jacket SuperEvac and :-\ I don't remember how much I paid for mine but it wasn't close to what they're selling for now. But poking around on Amazon it appears a 2 stage Robinair can be had for well under $200 and you could go much cheaper.

Gauges under a $100 including the 1/4">5/16" adapter you'll probably need.

So what you've got to have comes in under $500 and a good chunk of the tools are going to have other uses for most folks on this forum.

To do the job 100% by the book you should also have a micron gauge and high pressure inert gas but that's only another couple hundred dollars for the gauge and high pressure regulator, plus whatever the gas costs you. Personally I use the argon cylinder from my TIG for an inert gas source. And FWIW some pros will skip these parts.

I'm also scratching my head at your "reputable dealer" comment. If you're in the trade and can't find a reputable employer to work for how is a customer gonna find one?

Offline Matt_T

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Re: Ductless HVAC Systems
« Reply #9 on: May 04, 2019, 10:51:12 PM »
I've got an HVAC company that has taken care of my house for over 20 years and the Trane system installed over five years ago has been fault-free.  I have a maintenance contract with them for twice a year checkups and will use them for any new system I purchase.  For me it is worth any amount I would save.

If you do decide on a pro install talk to them and try to gauge how comfortable/familiar they are with minis. Our local Trane dealer is good on conventional systems but I wouldn't let them work on my minis. These things are a major technology leap compared to conventional air conditioners which intimidates/confuses a lot of hvac guys. If you go the pro route try to find someone who knows how to properly install and troubleshoot them.

Offline bonneyman

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Re: Ductless HVAC Systems
« Reply #10 on: May 04, 2019, 11:30:44 PM »
I'm also scratching my head at your "reputable dealer" comment. If you're in the trade and can't find a reputable employer to work for how is a customer gonna find one?

Well, it's a prefaced statement so I don't come across as high and mighty. I know arrogant owners, I don't want to be one.

I don't say licensed contractor because I know alot of licensed companies that I wouldn't have work on my dog house. Besides, virtually all licensed companies have one guy (i.e. the boss) who holds the license - but the person doing the actual work can be anywhere on a wide spectrum of knowledge, ethics, and workmanship. And I can't guarantee that those techs are doing it right.
When I say "reputable dealer" I mean one that your friends have used and has a good reputation. People who's houses you can visit and see the work that the guy did. TV ads don't tell the story, suave radio ads don't, shiny billboards don't. The proof is in the pudding. If your friends like the work that's been done - and th follow-up maintenance - that would be the guys I would recommend you hire.


Offline slip knot

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Re: Ductless HVAC Systems
« Reply #11 on: May 05, 2019, 11:31:16 AM »
I looked at these a year or so back as replacements for the window units in our rentals. I've got 6-8 window units running at one time and am replacing at least one per year. Heat/cool window units aren't cheap. Several people in the business recommended the Mitsubishi Mr slim units. they had really good luck with them and they came with a real good 5yr warranty IIRC. But the units were @$5000 for the size looked at. I looked at several other brands and they were a good bit cheaper but the warranty wasn't as good either. one thing I got from almost all of these was the warranty was void if you didn't have a factory trained installer put it in.

I had to put this project on hold for a while and will probably look at it agin when I have a vacant house again. I will go with a cheaper brand and do the install myself. I already have all the tools needed and it doesn't seem to complicated to install these things.

Offline Matt_T

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Re: Ductless HVAC Systems
« Reply #12 on: May 05, 2019, 10:19:39 PM »
I looked at these a year or so back as replacements for the window units in our rentals. I've got 6-8 window units running at one time and am replacing at least one per year. Heat/cool window units aren't cheap. Several people in the business recommended the Mitsubishi Mr slim units. they had really good luck with them and they came with a real good 5yr warranty IIRC. But the units were @$5000 for the size looked at. I looked at several other brands and they were a good bit cheaper but the warranty wasn't as good either. one thing I got from almost all of these was the warranty was void if you didn't have a factory trained installer put it in.

I had to put this project on hold for a while and will probably look at it agin when I have a vacant house again. I will go with a cheaper brand and do the install myself. I already have all the tools needed and it doesn't seem to complicated to install these things.

I think we discussed this some before the old site crashed. Reliability might be better but I wouldn't bet on it with cheaper units. And when one does fail it'll be more aggravation, and possibly more cost, compared to switching out a window shaker.

The main benefits of minis are improved comfort, much lower noise, and lower running costs. They're not generally cheaper than window shakers when it comes to upfront or lifetime equipment costs. Which leaves you with the costs and your tenants getting the benefits so I'm not convinced they're the best solution for you. To drift the thread slightly maybe adding baseboard electric heaters and switching to AC only window shakers would be a better way to improve reliability/reduce your cost?

But yeah they're not difficult to install so long as you're a do it right electro-mechanically inclined type. And if you're really concerned about warranty take a look at the Mr Cool DIY minis. You'll pay a bit of a premium for them compared to an equivalent unit but nothing like the cost of a pro install. Main downside of them is you're stuck with a 25 foot lineset which you'll have to find a way to deal with.

Offline bonneyman

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Re: Ductless HVAC Systems
« Reply #13 on: May 06, 2019, 10:49:44 AM »
Yeah, the pre-made line sets seem to always be short unless it's on a spare bedroom where the cond unit is on the opposite side of the wall from the evap unit. Some installs I've seen had longer linesets - but didn't need them - but the installer(homeowner?) didn't mess with shortening and fittings and just left the excess lines coiled up out near the cond unit.

Online skfarmer

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Re: Ductless HVAC Systems
« Reply #14 on: May 06, 2019, 12:10:05 PM »
I find this topic interesting. My sons house is cooled with 2 window units. One big unit that is "supposed" to cool the kitchen, living room and bathroom and a smaller unit for the master bedroom. He wants to replace the large unit with a DIY minisplit.

Guess who he wants to install it?
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